The present invention relates generally to control systems for diesel engines, and particularly to a system for regulating the loading of a diesel locomotive.
Conventional diesel engines, including, but not limited to those used in locomotives, are often provided with a range of preset throttle speeds available for selection by the operator. In the case of locomotives, to accelerate, the operator progresses sequentially through the range of preset throttle speeds. Acting in concert with the throttle adjustment is an engine loading system which is normally under computer control. Engine loading relates to the amount of fuel/air mixture which is sent to the engine to achieve a certain throttle speed. In one type of conventional diesel engine control system, a governor employing a power piston is used to regulate engine loading. The power piston controls the amount of fuel being distributed to the cylinders.
It has been found that when locomotives having the above-identified engine control system are employed at sea level, the engine loading function of the power piston operates satisfactorily. However, when such locomotives are operated at higher altitudes, the relatively thinner air causes the engine loading system to provide an excessively rich fuel/air mixture. An excessively rich mixture can also occur when the engine is not in proper tune. An undesirable and possibly hazardous side effect of the rich mixture is that the engine may emit transient smoke or fire.
Prior attempts to eliminate transient smoke or fire incorporate either analog or digital engine control systems which control engine loading by determining the amount of air available for combustion, and applying that value to sensed or computed values for engine speed, the amount of fuel being provided for combustion, and current engine loading. This operation results in an approximation of how much additional electrical load can be added. In instances where the engine begins to "bog", such systems have a function for removing some of the electrical load. It is also known to provide a "fuel limiter" to constrain the maximum amount of fuel that can be provided to the engine at any given time. It has been found that these prior attempts are less than totally satisfactory for reliable locomotive engine performance at a variety of elevations and under a wide range of environmental conditions.
Accordingly, a main object of the present invention is to provide a control system for a diesel engine which automatically adjusts engine loading in response to environmental conditions.
Another object of the present invention is to provide a control system for a diesel engine which senses conditions causing engine overloading, and automatically reduces loading a corresponding amount to avoid unwanted conditions such as transient smoke and fire.